U.S. patent application number 15/715225 was filed with the patent office on 2018-03-29 for medium and method of manufacturing electronic component.
The applicant listed for this patent is Murata Manufacturing Co., Ltd.. Invention is credited to Shuichi ITO, Hirokazu YAMAOKA.
Application Number | 20180090276 15/715225 |
Document ID | / |
Family ID | 61686604 |
Filed Date | 2018-03-29 |
United States Patent
Application |
20180090276 |
Kind Code |
A1 |
ITO; Shuichi ; et
al. |
March 29, 2018 |
MEDIUM AND METHOD OF MANUFACTURING ELECTRONIC COMPONENT
Abstract
A medium is accommodated in a container together with an
electronic component body including an underlying electrode layer.
The medium treats a surface of the underlying electrode layer while
vibration is applied to the container. The medium is spherical or
substantially spherical. The medium has a diameter not smaller than
about 0.2 mm and not greater than about 2.0 mm. The medium contains
tungsten.
Inventors: |
ITO; Shuichi;
(Nagaokakyo-shi, JP) ; YAMAOKA; Hirokazu;
(Nagaokakyo-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Murata Manufacturing Co., Ltd. |
Nagaokakyo-shi |
|
JP |
|
|
Family ID: |
61686604 |
Appl. No.: |
15/715225 |
Filed: |
September 26, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01G 4/232 20130101;
H01G 4/248 20130101; H01G 4/0085 20130101; H01G 4/30 20130101 |
International
Class: |
H01G 4/30 20060101
H01G004/30; H01G 4/248 20060101 H01G004/248; H01G 4/008 20060101
H01G004/008; H01G 4/232 20060101 H01G004/232 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2016 |
JP |
2016-189409 |
Sep 28, 2016 |
JP |
2016-189410 |
Mar 24, 2017 |
JP |
2017-059151 |
Claims
1. A method of manufacturing an electronic component comprising:
introducing a plurality of multilayer bodies and media into a
container, the plurality of multilayer bodies each including a
first end surface and a second end surface opposed to each other in
a direction of length, a first side surface and a second side
surface opposed to each other in a direction of width perpendicular
or substantially perpendicular to the direction of length, and a
first main surface and a second main surface opposed to each other
in a direction of height perpendicular or substantially
perpendicular to the direction of length and the direction of
width, the first end surface being provided with a first baked
electrode layer, and the second end surface being provided with a
second baked electrode layer; and applying vibration energy to the
plurality of multilayer bodies and the media by applying vibration
to the container, the container including a bottom portion and a
circumferential wall portion connected to a circumferential edge of
the bottom portion; wherein when an annular virtual axis
circumferentially surrounding a central axis of the bottom portion
is assumed in a state before vibration of the container, in the
applying vibration energy to the plurality of multilayer bodies and
the media, vibration is applied to the multilayer bodies and the
media such that the multilayer bodies and the media follow a
helical trace helically surrounding the virtual axis along an axial
direction of the virtual axis.
2. The method of manufacturing an electronic component according to
claim 1, wherein a frequency of the vibration applied to the
container resonates with a natural frequency of the container.
3. The method of manufacturing an electronic component according to
claim 1, wherein each of the first baked electrode layer and the
second baked electrode layer includes a material containing any one
of Cu, Ag, Ni, Pd, an Ag-Pd alloy, and Au.
4. The method of manufacturing an electronic component according to
claim 1, wherein a total of volumes of the plurality of multilayer
bodies introduced into the container is at most about 1/2 of a
total of volumes of the media introduced into the container.
5. The method of manufacturing an electronic component according to
claim 1, wherein each of the media is spherical or substantially
spherical.
6. The method of manufacturing an electronic component according to
claim 1, wherein each of the media has a diameter not smaller than
about 0.2 mm and not greater than about 2.0 mm.
7. The method of manufacturing an electronic component according to
claim 1, wherein each of the media includes tungsten.
8. The method of manufacturing an electronic component according to
claim 1, wherein each of the media has a surface roughness Sa not
greater than about 190 nm.
9. The method of manufacturing an electronic component according to
claim 1, wherein each of the media has a specific gravity not lower
than 5 and not higher than 18.
10. The method of manufacturing an electronic component according
to claim 1, wherein each of the media has a diameter not smaller
than about 0.4 mm and not greater than about 1.0 mm.
11. The method of manufacturing an electronic component according
to claim 1, wherein each of the media includes cobalt and/or
chromium.
12. The method of manufacturing an electronic component according
to claim 1, wherein the electronic component is one of a multilayer
ceramic capacitor, a piezoelectric component, a thermistor, and an
inductor.
13. A medium used in forming an external electrode including an
underlying electrode layer in an electronic component body, the
medium being accommodated in a container together with the
electronic component body including the underlying electrode layer
and treating a surface of the underlying electrode layer as a
result of application of vibration to the container; wherein the
medium is spherical or substantially spherical; the medium has a
diameter not smaller than about 0.2 mm and not greater than about
2.0 mm; and the medium includes tungsten.
14. The medium according to claim 13, wherein the medium has a
surface roughness Sa not greater than about 190 nm.
15. The medium according to claim 13, wherein the medium has a
specific gravity not lower than 5 and not higher than 18.
16. The medium according to claim 13, wherein the medium has a
diameter not smaller than about 0.4 mm and not greater than about
1.0 mm.
17. The medium according to claim 13, wherein the medium includes
cobalt and/or chromium.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority to Japanese
Patent Application No. 2016-189409 filed on Sep. 28, 2016, Japanese
Patent Application No. 2016-189410 filed on Sep. 28, 2016 and
Japanese Patent Application No. 2017-059151 filed on Mar. 24, 2017.
The entire contents of these applications are hereby incorporated
herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to a medium used in forming an
external electrode including a baked electrode layer in an
electronic component body and a method of manufacturing an
electronic component.
2. Description of the Related Art
[0003] For example, Japanese Patent Laying-Open No. 2012-134286
discloses a method of manufacturing a multilayer ceramic capacitor
as an electronic component. In the method of manufacturing a
multilayer ceramic capacitor disclosed in Japanese Patent
Laying-Open No. 2012-134286, a paste contained in glass is attached
to an end surface of a multilayer body as an electronic component
body substantially in a shape of a parallelepiped by immersing the
end surface in the paste. By baking the paste attached to the end
surface after drying the paste, a baked electrode layer as an
underlying electrode which forms a part of an external electrode is
provided on the end surface. Thereafter, a glass component which
has floated up to a surface of the baked electrode layer is
removed.
[0004] In the method of manufacturing a multilayer ceramic
capacitor disclosed in Japanese Patent Laying-Open No. 2012-134286,
sandblasting is used for removal of the glass component. In
sandblasting, a plurality of multilayer bodies are placed in a
barrel and the barrel is rotated while abrasive powders are blown
from the outside of the barrel. Since excessive force is applied to
the multilayer bodies as a result of rotation of the barrel, the
multilayer bodies are chipped and characteristics as a capacitor
may not be satisfied.
[0005] A state of a surface of the baked electrode layer polished
in sandblasting is poor and the baked electrode layer may peel off
in a corner portion of the multilayer body.
SUMMARY OF THE INVENTION
[0006] Preferred embodiments of the present invention provide
methods of manufacturing electronic components that achieve
significantly reduced or no fracture and chipping of a multilayer
body and reform a surface of a baked electrode layer provided in
the multilayer body.
[0007] Preferred embodiments of the present invention also provide
media that are able to reform a surface of an underlying electrode
layer provided in an electronic component body.
[0008] A method of manufacturing an electronic component according
to a preferred embodiment of the present invention includes
introducing a plurality of multilayer bodies and media into a
container, the plurality of multilayer bodies each including a
first end surface and a second end surface opposed to each other in
a direction of length, a first side surface and a second side
surface opposed to each other in a direction of width perpendicular
or substantially perpendicular to the direction of length, and a
first main surface and a second main surface opposed to each other
in a direction of height perpendicular or substantially
perpendicular to the direction of length and the direction of
width, the first end surface being provided with a first baked
electrode layer, and the second end surface being provided with a
second baked electrode layer, and applying vibration energy to the
plurality of multilayer bodies and the media. A container including
a bottom portion and a circumferential wall portion connected to a
circumferential edge of the bottom portion is used as the
container. When an annular virtual axis circumferentially
surrounding a central axis of the bottom portion is assumed in a
state before vibration of the container, in the applying vibration
energy to the plurality of multilayer bodies and the media,
vibration is applied to the multilayer bodies and the media such
that the multilayer bodies and the media follow a helical trace
helically surrounding the virtual axis along an axial direction of
the virtual axis.
[0009] In a method of manufacturing an electronic component
according to a preferred embodiment of the present invention, a
frequency of the vibration applied to the container resonates with
a natural frequency of the container.
[0010] In a method of manufacturing an electronic component
according to a preferred embodiment of the present invention,
preferably, a material containing any metal of Cu, Ag, Ni, Pd, an
Ag-Pd alloy, and Au is used for the first baked electrode layer and
the second baked electrode layer.
[0011] In a method of manufacturing an electronic component
according to a preferred embodiment of the present invention,
preferably, a total of volumes of the plurality of multilayer
bodies introduced into the container is at most about 1/2 of a
total of volumes of the media introduced into the container.
[0012] A medium according to a preferred embodiment of the present
invention is used in forming an external electrode including an
underlying electrode layer in an electronic component body. The
medium is accommodated in a container together with the electronic
component body including the underlying electrode layer. The medium
treats a surface of the underlying electrode layer as a result of
application of vibration to the container. The medium is spherical
or substantially spherical. The medium has a diameter not smaller
than about 0.2 mm and not greater than about 2.0 mm, for example.
The medium contains tungsten.
[0013] A medium according to a preferred embodiment of the present
invention preferably has surface roughness Sa not greater than
about 190 nm, for example.
[0014] A medium according to a preferred embodiment of the present
invention preferably has a specific gravity not lower than 5 and
not higher than 18.
[0015] A medium according to a preferred embodiment of the present
invention preferably has a diameter not smaller than about 0.4 mm
and not greater than about 1.0 mm.
[0016] A medium according to a preferred embodiment of the present
invention preferably further includes cobalt and/or chromium.
[0017] The above and other elements, features, steps,
characteristics and advantages of the present invention will become
more apparent from the following detailed description of the
preferred embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a perspective view of a multilayer ceramic
capacitor manufactured in accordance with a method of manufacturing
a multilayer ceramic capacitor according to a first preferred
embodiment of the present invention.
[0019] FIG. 2 is a cross-sectional view along the line II-II of the
multilayer ceramic capacitor shown in FIG. 1.
[0020] FIG. 3 is a cross-sectional view along the line III-III of
the multilayer ceramic capacitor shown in FIG. 1.
[0021] FIG. 4 is a partial cross-sectional view showing details of
a baked electrode layer of the multilayer ceramic capacitor
according to the first preferred embodiment of the present
invention.
[0022] FIG. 5 is a flowchart showing the method of manufacturing a
multilayer ceramic capacitor according to the first preferred
embodiment of the present invention.
[0023] FIG. 6 is a diagram showing a surface treatment apparatus
for performing surface treatment of the baked electrode layer shown
in FIG. 5.
[0024] FIG. 7 is a plan view of an agitation vessel shown in FIG.
6.
[0025] FIG. 8 is a cross-sectional view of the agitation vessel
shown in FIG. 6.
[0026] FIG. 9 is a plan view showing positional relation between
the agitation vessel shown in FIG. 6 and an elastic member.
[0027] FIG. 10 is a flowchart showing details of a step of surface
treatment of the baked electrode layer shown in FIG. 5.
[0028] FIG. 11 is a diagram showing a step of applying vibration
energy to a plurality of multilayer bodies and media in the step of
applying vibration to the agitation vessel shown in FIG. 10.
[0029] FIG. 12 is a partial cross-sectional view showing details of
a baked electrode layer of a multilayer ceramic capacitor
manufactured in accordance with a method of manufacturing a
multilayer ceramic capacitor according to a second preferred
embodiment of the present invention.
[0030] FIG. 13 is a cross-sectional view of a multilayer ceramic
capacitor manufactured in accordance with a method of manufacturing
a multilayer ceramic capacitor according to a third preferred
embodiment of the present invention.
[0031] FIG. 14 is a flowchart showing the method of manufacturing a
multilayer ceramic capacitor according to the third preferred
embodiment of the present invention.
[0032] FIG. 15 is a diagram showing a condition and a result in a
first verification experiment conducted for verifying advantageous
effects of the preferred embodiments of the present invention.
[0033] FIG. 16 is a diagram showing a state of a surface of a baked
electrode layer before surface treatment in Example 2 shown in FIG.
15.
[0034] FIG. 17 is a diagram showing a state of the surface of the
baked electrode layer after surface treatment in Example 2 shown in
FIG. 15.
[0035] FIG. 18 is a diagram showing as a reference example, a state
of a surface of a baked electrode layer after surface treatment
with the use of a medium composed of zirconium.
[0036] FIG. 19 is a cross-sectional view showing a state of the
baked electrode layer in the vicinity of a corner portion before
surface treatment in Example 2 shown in FIG. 15.
[0037] FIG. 20 is a cross-sectional view showing a state of the
baked electrode layer in the vicinity of the corner portion after
surface treatment in Example 2 shown in FIG. 15.
[0038] FIG. 21 is a cross-sectional view showing a state of the
baked electrode layer in a central portion of an end surface before
surface treatment in Example 2 shown in FIG. 15.
[0039] FIG. 22 is a cross-sectional view showing a state of the
baked electrode layer in the central portion of the end surface
after surface treatment in Example 2 shown in FIG. 15.
[0040] FIG. 23 is a diagram showing a condition and a result of a
second verification experiment conducted for verifying advantageous
effects of the preferred embodiments of the present invention.
[0041] FIG. 24 is a diagram showing one example of surface
roughness of a medium used in the second verification
experiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0042] Preferred embodiments of the present invention will be
described below in detail with reference to the drawings. The
preferred embodiments shown below exemplify a multilayer ceramic
capacitor as an electronic component and exemplify a method of
manufacturing a multilayer ceramic capacitor as a method of
manufacturing an electronic component. In the preferred embodiments
shown below, the same or common elements have the same reference
characters allotted and description thereof will not be
repeated.
First Preferred Embodiment
[0043] Prior to describing a method of manufacturing a multilayer
ceramic capacitor according to a preferred embodiment of the
present invention, initially, a multilayer ceramic capacitor
manufactured in accordance with the manufacturing method will be
described.
[0044] FIG. 1 is a perspective view of a multilayer ceramic
capacitor manufactured in accordance with a method of manufacturing
a multilayer ceramic capacitor according to a first preferred
embodiment. FIG. 2 is a cross-sectional view along the line II-II
of the multilayer ceramic capacitor shown in FIG. 1. FIG. 3 is a
cross-sectional view along the line III-III of the multilayer
ceramic capacitor shown in FIG. 1.
[0045] As shown in FIGS. 1 to 3, a multilayer ceramic capacitor 10
includes a multilayer body 12 defining an electronic component
body, a first external electrode 15, and a second external
electrode 16.
[0046] Multilayer body 12 has an outer geometry substantially in a
shape of a parallelepiped. Multilayer body 12 includes a plurality
of dielectric layers 13 and a plurality of internal electrode
layers 14 which are stacked on one another. Multilayer body 12
includes a first side surface 12c and a second side surface 12d as
being opposed to each other in a direction of width W, a first main
surface 12a and a second main surface 12b as being opposed to each
other in a direction of height T perpendicular or substantially
perpendicular to direction of width W, and a first end surface 12e
and a second end surface 12f as being opposed to each other in a
direction of length L perpendicular or substantially perpendicular
to both of direction of width W and direction of height T.
[0047] Though multilayer body 12 has an outer geometry
substantially in a shape of a parallelepiped, it preferably
includes a corner portion and a ridgeline portion rounded. The
corner portion is a portion where three surfaces of multilayer body
12 meet one another and the ridgeline portion is a portion where
two surfaces of multilayer body 12 meet each other. Projections and
recesses may be provided in at least any one of first main surface
12a, second main surface 12b, first side surface 12c, second side
surface 12d, first end surface 12e, and second end surface 12f.
[0048] The outer geometry of multilayer body 12 has, for example, a
dimension in the direction of length L not smaller than about 0.2
mm and not greater than about 5.7 mm, a dimension in the direction
of width W not smaller than about 0.1 mm and not greater than about
5.0 mm, and a dimension in the direction of height T not smaller
than about 0.1 mm and not greater than about 5.0 mm. The dimension
of the outer geometry of multilayer ceramic capacitor 10 can be
measured with a micrometer.
[0049] Multilayer body 12 is divided into a pair of outer portions
and an inner portion in the direction of height T. One of the pair
of outer portions is a portion including first main surface 12a of
multilayer body 12 and includes dielectric layer 13 located between
first main surface 12a and a first internal electrode layer 141
closest to first main surface 12a which will be described later.
The other of the pair of outer portions is a portion including
second main surface 12b of multilayer body 12 and includes
dielectric layer 13 located between second main surface 12b and a
second internal electrode layer 142 closest to second main surface
12b which will be described later.
[0050] The inner portion is a region lying between the pair of
outer portions. The inner portion includes a plurality of
dielectric layers 13 not defining the outer portions and all
internal electrode layers 14.
[0051] The number of stacked dielectric layers 13 is preferably not
smaller than 20 and not greater than 1000. Each of the pair of
outer portions has a thickness preferably not smaller than about 30
.mu.m and not greater than about 850 .mu.m, for example. Each of
the plurality of dielectric layers 13 included in the inner portion
has a thickness preferably not smaller than about 0.3 .mu.m and not
greater than about 30 .mu.m, for example.
[0052] Dielectric layer 13 is composed of a perovskite-type
compound containing Ba or Ti. Dielectric ceramics mainly composed
of BaTiO.sub.3, CaTiO.sub.3, SrTiO.sub.3, or CaZrO.sub.3 can be
used as a material to form dielectric layer 13. A material in which
a sub component such as an Mn compound, an Mg compound, an Si
compound, an Fe compound, a Cr compound, a Co compound, an Ni
compound, an Al compound, a V compound, or a rare-earth compound is
added to such a main component may be used.
[0053] A plurality of internal electrode layers 14 include a
plurality of first internal electrode layers 141 connected to first
external electrode 15 and a plurality of second internal electrode
layers 142 connected to second external electrode 16.
[0054] The number of stacked internal electrode layers 14 is
preferably not smaller than 10 and not greater than 1000. Each of
the plurality of internal electrode layers 14 has a thickness
preferably not smaller than about 0.3 .mu.m and not greater than
about 1.0 .mu.m, for example.
[0055] One metal selected from the group consisting of Ni, Cu, Ag,
Pd, and Au can be used as a material for internal electrode layer
14. Internal electrode layer 14 may contain particles of a
dielectric identical in composition base to dielectric ceramics
contained in dielectric layer 13.
[0056] First internal electrode layer 141 and second internal
electrode layer 142 are alternately arranged at a regular interval
in the direction of width W of multilayer body 12. First internal
electrode layer 141 and second internal electrode layer 142 are
arranged as being opposed to each other with dielectric layer 13
being interposed.
[0057] First internal electrode layer 141 includes a first opposed
electrode portion opposed to second internal electrode layer 142
and a first extracted electrode portion extracted from the first
opposed electrode portion toward first end surface 12e of
multilayer body 12.
[0058] Second internal electrode layer 142 includes a second
opposed electrode portion opposed to first internal electrode layer
141 and a second extracted electrode portion extracted from the
second opposed electrode portion toward second end surface 12f of
multilayer body 12.
[0059] Dielectric layer 13 is located between the opposed electrode
portion of first internal electrode layer 141 and the opposed
electrode portion of second internal electrode layer 142 so that a
capacitance is generated. A function of a capacitor is thus
provided.
[0060] In multilayer body 12, when viewed in the direction of
height T of multilayer body 12, a position between the opposed
electrode portion and first side surface 12c is defined as a first
side margin and a position between the opposed electrode portion
and second side surface 12d is defined as a second side margin.
When viewed in the direction of height T of multilayer body 12, a
position between the opposed electrode portion and first end
surface 12e is defined as a first end margin and a position between
the opposed electrode portion and second end surface 12f is defined
as a second end margin.
[0061] The first end margin includes the first extracted electrode
portion of first internal electrode layer 141 and a plurality of
dielectric layers 13 adjacent thereto. The second end margin
includes the second extracted electrode portion of second internal
electrode layer 142 and a plurality of dielectric layers 13
adjacent thereto.
[0062] First external electrode 15 is provided on first end surface
12e. More specifically, first external electrode 15 extends from
first end surface 12e to first main surface 12a and second main
surface 12b as well as to first side surface 12c and second side
surface 12d.
[0063] Second external electrode 16 is provided on second end
surface 12f. More specifically, second external electrode 16
extends from second end surface 12f to first main surface 12a and
second main surface 12b as well as to first side surface 12c and
second side surface 12d.
[0064] First external electrode 15 includes a first baked electrode
layer 15a as an underlying electrode layer and a plating layer 15b
and a plating layer 15c provided on first baked electrode layer
15a.
[0065] Second external electrode 16 includes a second baked
electrode layer 16a as an underlying electrode layer and a plating
layer 16b and a plating layer 16c provided on second baked
electrode layer 16a.
[0066] First baked electrode layer 15a and second baked electrode
layer 16a contain pores and glass and a metal. Examples of the
metal contained in first baked electrode layer 15a and second baked
electrode layer 16a include an appropriate metal such as Ni, Cu,
Ag, Pd, Au, and an Ag-Pd alloy. Highly malleable Cu and Ag are
suitably used as the metal. A metal contained in first baked
electrode layer 15a and second baked electrode layer 16a can be
determined with a wavelength-dispersive X-ray spectroscope (WDX)
after multilayer ceramic capacitor 10 is polished. In polishing,
for example, a cross-section perpendicular or substantially
perpendicular to direction of width W is exposed by polishing
multilayer ceramic capacitor 10 to a position in the center in the
direction of width W.
[0067] First baked electrode layer 15a and second baked electrode
layer 16a may include a plurality of stacked layers. First baked
electrode layer 15a and second baked electrode layer 16a are layers
obtained by applying a conductive paste containing glass and a
metal to multilayer body 12 and baking the conductive paste. First
baked electrode layer 15a and second baked electrode layer 16a may
be formed by being fired simultaneously with internal electrode
layer 14 or by being baked after firing of internal electrode layer
14.
[0068] First baked electrode layer 15a and second baked electrode
layer 16a have a maximum thickness preferably not smaller than
about 10 .mu.m and not greater than about 200 .mu.m, for example. A
thickness of first baked electrode layer 15a and second baked
electrode layer 16a is small in a corner portion of multilayer body
12.
[0069] Details of first baked electrode layer 15a and second baked
electrode layer 16a will be described later with reference to FIG.
4.
[0070] Plating layers 15b, 15c, 16b, and 16c are composed of one
metal selected from the group consisting of Ni, Cu, Ag, Pd, Au, and
Sn or an alloy containing such a metal.
[0071] For example, plating layer 15b and plating layer 16b are Ni
plating layers and plating layers 15c and 16c are, for example, Sn
plating layers. The Ni plating layer has a function to prevent the
underlying electrode layer from being eroded by solder in mounting
of a multilayer ceramic capacitor. The Sn plating layer has a
function to improve solderability in mounting of a multilayer
ceramic capacitor and to facilitate mounting of the multilayer
ceramic capacitor. One plating layer has a thickness preferably not
smaller than about 1.5 .mu.m and not greater than about 15.0 .mu.m,
for example. The plating layer may include a single layer, and may
include a Cu plating layer or an Au plating layer.
[0072] FIG. 4 is a partial cross-sectional view showing details of
the baked electrode layer of the multilayer ceramic capacitor
according to the first preferred embodiment. A circular object
included in first baked electrode layer 15a shown in FIG. 4
represents a pore or glass. Details of first baked electrode layer
15a will be described with reference to FIG. 4. Since second baked
electrode layer 16a is similar in construction to first baked
electrode layer 15a, description thereof will not be provided.
[0073] As shown in FIG. 4, first baked electrode layer 15a includes
a first region 15a1 and a second region 15a2 from a side of
multilayer body 12 toward a surface layer of first baked electrode
layer 15a.
[0074] First region 15a1 contains pores and glass to a considerable
extent. First region 15a1 occupies a major portion of first baked
electrode layer 15a. As first region 15a1 contains pores, first
baked electrode layer 15a has cushioning properties. External
impact applied to multilayer ceramic capacitor 10 is thus able to
be absorbed.
[0075] Second region 15a2 is high in density of a metal in a
direction of thickness from a surface layer. Second region 15a2
contains substantially no glass and pores. A surface of second
region 15a2 is constructed to be smooth. Second region 15a2 has a
thickness at least not smaller than about 0.1 .mu.m and not greater
than about 10 .mu.m, for example. By setting a thickness of second
region 15a2 to about 0.1 .mu.m or greater and forming a dense metal
film on the surface of the first baked electrode layer and the
second baked electrode layer, attaching properties of plating are
able to be improved or intrusion by plating is able to be
significantly reduced or prevented, and therefore reliability of
multilayer ceramic capacitor 10 is significantly improved. As will
be described later, second region 15a2 is provided by using a
surface treatment apparatus 100 (see FIG. 6) to rub a medium 20
(see FIG. 11) against a surface layer of a baked electrode.
Therefore, by setting a thickness of second region 15a2 to about 10
.mu.m or smaller, damage to multilayer body 12 is able to be
significantly reduced or prevented, and chipping and fracture of
multilayer body 12 are significantly reduced or prevented.
[0076] A thickness of second region 15a2 can be measured through
observation with an SEM after multilayer ceramic capacitor 10 is
polished. Specifically, for example, a cross-section along
direction of length L and direction of height T is exposed by
polishing multilayer ceramic capacitor 10 to a position
approximately 1/2 of a dimension in the direction of width W, and a
thickness from a corner portion connecting first end surface 12e
and first main surface 12a to each other to a vertex of second
region 15a2 located on the corner portion is measured. An average
value of thicknesses of second regions 15a2 obtained from ten
multilayer ceramic capacitors 10 is preferably defined as a
thickness of second region 15a2.
[0077] Second region 15a2 covers first region 15a1. Second region
15a2 high in density of the metal is provided on a side of the
surface layer so that moisture resistance of multilayer body 12 is
able to be improved. The surface of second region 15a2 is
constructed to be smooth so that occurrence of a defect in plating
layer 15b and plating layer 15c in formation of plating layer 15b
and plating layer 15c is able to significantly reduced or
prevented. Continuity between plating layer 15b and plating layer
15c is able to be improved.
[0078] Second region 15a2 is formed by subjecting first baked
electrode layer 15a and second baked electrode layer 16a to surface
treatment in a step of surface treatment of the baked electrode
layer which will be described later.
[0079] FIG. 5 is a flowchart showing the method of manufacturing a
multilayer ceramic capacitor according to the first preferred
embodiment. The method of manufacturing a multilayer ceramic
capacitor according to the first preferred embodiment will be
described with reference to FIG. 5.
[0080] As shown in FIG. 5, in manufacturing multilayer ceramic
capacitor 10, initially, in a step S1, ceramic dielectric slurry is
prepared. Specifically, the ceramic dielectric slurry is prepared
by mixing ceramic dielectric powders, additive powders, and a
binder resin with a solution as being dispersed therein. The
ceramic dielectric slurry may be based on any of a solvent and
water. When a water-based paint is used for the ceramic dielectric
slurry, the ceramic dielectric slurry is prepared by mixing a
water-soluble binder and a dispersant with a dielectric source
material dissolved in water.
[0081] Then, in a step S2, a ceramic dielectric sheet is formed.
Specifically, the ceramic dielectric sheet is formed by forming the
ceramic dielectric slurry into a sheet on a carrier film by using a
die coater, a gravure coater, or a microgravure coater and drying
the ceramic dielectric slurry. The ceramic dielectric sheet has a
thickness preferably not greater than about 3 .mu.m from a point of
view of reduction in size and a higher capacity of multilayer
ceramic capacitor 10, for example.
[0082] Then, in a step S3, a mother sheet is formed. Specifically,
a mother sheet provided with a prescribed internal electrode
pattern is provided on the ceramic dielectric sheet by applying a
conductive paste to the ceramic dielectric sheet to have a
prescribed pattern. Screen printing, ink jet printing, or gravure
printing can be used as a method of applying the conductive paste.
The internal electrode pattern has a thickness preferably not
greater than about 1.5 .mu.m from a point of view of reduction in
size and a higher capacity of multilayer ceramic capacitor 10, for
example. In addition to the mother sheet having an internal
electrode pattern, a ceramic dielectric sheet which is not
subjected to step S3 is also prepared as the mother sheet.
[0083] Then, in a step S4, a plurality of mother sheets are
stacked. Specifically, a prescribed number of mother sheets not
having the internal electrode pattern formed thereon but consisting
of the ceramic dielectric sheet are stacked. A prescribed number of
mother sheets provided with the internal electrode pattern are
stacked thereon. A prescribed number of mother sheets not having
the internal electrode pattern formed thereon but consisting of the
ceramic dielectric sheet are further stacked thereon. A mother
sheet group is thus formed.
[0084] Then, in a step S5, a multilayer block is formed by pressure
bonding the mother sheet group. Specifically, the multilayer block
is formed by applying a pressure to the mother sheet group in a
direction of stack by a hydrostatic press or a rigid press to
pressure-bond the mother sheet group.
[0085] Then, in a step S6, multilayer chips are formed by dividing
the multilayer block. Specifically, the multilayer block is divided
into a matrix by cutting by pushing, dicing, or laser cutting, so
that the multilayer block is divided into a plurality of individual
multilayer chips.
[0086] Then, in a step S7, the multilayer chips are subjected to
barrel polishing. Specifically, the multilayer chips are polished
by sealing the multilayer chips in a small box called a barrel
together with medium balls higher in hardness than a dielectric
material and rotating the barrel. The corner portion and the
ridgeline portion of the multilayer chip are thus rounded.
[0087] Then, in a step S8, the multilayer chip is fired.
Specifically, multilayer body 12 is formed by heating the
multilayer chip and thus firing a dielectric material and a
conductive material contained in the multilayer chip. A temperature
for firing is set as appropriate in accordance with the dielectric
material and the conductive material and is preferably not lower
than about 900.degree. C. and not higher than about 1300.degree.
C., for example.
[0088] Then, in a step S9, a conductive paste is applied to first
end surface 12e and second end surface 12f of multilayer body 12
through immersion. The conductive paste contains glass and a
disappearing agent such as a resin in addition to conductive fine
particles.
[0089] Then, in a step S10, the conductive paste applied to
multilayer body 12 is dried. Specifically, the conductive paste is
dried with hot air for approximately ten minutes, for example, at a
temperature not lower than about 60.degree. C. and not higher than
about 180.degree. C.
[0090] Then, in a step S11, the dried conductive paste is baked. A
temperature for baking is preferably not lower than about
700.degree. C. and not higher than about 900.degree. C. In this
baking step, the disappearing agent disappears so that a plurality
of pores are formed in the baked electrode layer. In a state after
step S11, the baked electrode layer is in a state of first region
15a1 described above from the side of multilayer body 12 toward the
surface layer. The side of the surface layer of the baked electrode
layer is also provided with pores and contains glass.
[0091] Then, in a step S12, the baked electrode layer is subjected
to surface treatment. The surface layer of the baked electrode
layer is polished by rubbing media 20 which will be described later
(see FIG. 11) against the surface layer of the baked electrode
layer by agitating the multilayer bodies provided with the baked
electrode layer and media 20 in an agitation vessel 150 which will
be described later. Glass contained in the surface layer of the
baked electrode is thus reduced and the surface layer of the baked
electrode layer is planarized. Consequently, a state of the surface
layer of the baked electrode layer is reformed and second region
15a2 described above which is high in density of the metal and has
a smooth surface is formed. Details of surface treatment will be
described with reference to FIGS. 6 to 10.
[0092] FIG. 6 is a diagram showing the surface treatment apparatus
for performing surface treatment of the baked electrode layer shown
in FIG. 5. FIG. 7 is a plan view of the agitation vessel shown in
FIG. 6. FIG. 8 is a cross-sectional view of the agitation vessel
shown in FIG. 6. FIG. 9 is a plan view showing positional relation
between the agitation vessel shown in FIG. 6 and an elastic member.
Surface treatment apparatus 100 used in step S12 will be described
with reference to FIGS. 6 to 9.
[0093] As shown in FIG. 6, surface treatment apparatus 100 includes
a first base portion 110, a second base portion 120, a third base
portion 130, a vibration reception plate 140, agitation vessel 150
as a container, a drive motor 160, an eccentric load 170, a
plurality of elastic members 180, a drive motor support portion
190, a sensor 200 which senses a state of vibration of agitation
vessel 150, and a drive motor controller 210.
[0094] First base portion 110 is in a shape of a plate. First base
portion 110 defines a lower portion of surface treatment apparatus
100. First base portion 110 is placed on a floor surface and keeps
levelness of surface treatment apparatus 100.
[0095] Second base portion 120 is substantially in a shape of a
parallelepiped. Second base portion 120 defines and functions as a
base to support loads imposed by vibration reception plate 140 and
agitation vessel 150 as well as drive motor 160 and eccentric load
170 supported on vibration reception plate 140. Second base portion
120 is constructed such that drive motor 160 is able to pass
therethrough.
[0096] Third base portion 130 is in a shape of a plate. Third base
portion 130 is carried on second base portion 120. Third base
portion 130 is constructed such that drive motor 160 is able to
pass therethrough.
[0097] First base portion 110, second base portion 120, and third
base portion 130 may be formed of independent different members or
may be formed integrally.
[0098] Vibration reception plate 140 is substantially in a shape of
a plate. Vibration reception plate 140 is supported by a plurality
of elastic members 180. Drive motor support portion 190 is provided
on a lower surface side of vibration reception plate 140. Drive
motor support portion 190 supports drive motor 160 to which
eccentric load 170 is rotatably attached. Loads imposed by drive
motor 160 and eccentric load 170 are thus applied to vibration
reception plate 140 with drive motor support portion 190 being
interposed.
[0099] An agitation vessel carrying portion 145 is provided on an
upper surface side of vibration reception plate 140. Agitation
vessel 150 is carried on agitation vessel carrying portion 145.
[0100] As shown in FIGS. 6 to 8, agitation vessel 150 is in a shape
of a cylinder with a bottom. Agitation vessel 150 includes a bottom
portion 151, a circumferential wall portion 152, a shaft portion
155, and a flange portion 156.
[0101] Bottom portion 151 is substantially in a shape of a disc.
Bottom portion 151 is constructed to be flat. Bottom portion 151
does not have to be flat. Circumferential wall portion 152 is
connected to a circumferential edge of bottom portion 151.
Circumferential wall portion 152 is erected upward from the
circumferential edge of bottom portion 151. Circumferential wall
portion 152 includes a curved portion 153 connected to bottom
portion 151 and a cylindrical portion 154 which linearly extends
along a vertical direction. Flange portion 156 protruding in a
radial direction is provided at an upper end of cylindrical portion
154.
[0102] Shaft portion 155 is provided in a central portion of bottom
portion 151. Shaft portion 155 extends along the vertical
direction. Shaft portion 155 does not have to be provided.
[0103] Agitation vessel 150 is not limited to the shape of the
cylinder with the bottom, and may be in a shape of a hemisphere or
a bowl. When agitation vessel 150 is hemispherical, bottom portion
151 forms a lower side of the hemisphere and circumferential wall
portion 152 defines an upper side of the hemisphere. Alternatively,
when agitation vessel 150 is in a shape of a bowl, it has such a
curved shape that bottom portion 151 expands downward.
[0104] As will be described later, a plurality of multilayer bodies
each having the baked electrode layer formed and media 20 are
introduced into agitation vessel 150.
[0105] A flexible coating layer made of urethane or the like is
preferably provided on an inner surface of agitation vessel 150. In
particular, when a large multilayer body of which length dimension
is greater than about 2.0 mm, width dimension is greater than about
1.2 mm, and thickness dimension is greater than about 1.2 mm is
handled, chipping and fracture of the multilayer body may occur and
hence an elastic member such as rubber is preferably used as a
coating layer.
[0106] When a small multilayer body of which length dimension is
not greater than about 2.0 mm, width dimension is not greater than
about 1.2 mm, and thickness dimension is not greater than about 1.2
mm is handled, concerns about fracture and chipping are less and
hence a coating layer does not have to be provided.
[0107] Agitation vessel 150 is preferably removably carried on
agitation vessel carrying portion 145. When a small multilayer body
as described above is handled, the inside of agitation vessel 150
is able to be cleaned by removing agitation vessel 150. Thus,
introduction of chips is prevented.
[0108] Agitation vessel 150, agitation vessel carrying portion 145,
and vibration reception plate 140 may be formed separately or
integrally.
[0109] As shown in FIGS. 6 and 9, a plurality of elastic members
180 are arranged at a prescribed pitch in a circumferential
direction around shaft portion 155 when viewed in a direction of
extension of shaft portion 155. The plurality of elastic members
180 are fixed onto base portion 130.
[0110] As shown in FIG. 6, drive motor 160 includes a rotation
shaft 161 extending in the vertical direction. Drive motor 160
rotates eccentric load 170 attached to rotation shaft 161 around
the rotation shaft by rotating rotation shaft 161.
[0111] As a position of the center of gravity of vibration
reception plate 140 is varied with rotation of eccentric load 170,
extension and contraction of the plurality of elastic members 180
becomes uneven. By making use of such uneven extension and
contraction of the plurality of elastic members 180, agitation
vessel 150 is able to be caused to vibrate as described above.
[0112] Sensor 200 senses a state of vibration of agitation vessel
150. A result of sensing by sensor 200 is input to drive motor
controller 210. For example, an acceleration sensor or a laser
displacement sensor is used as sensor 200.
[0113] When an acceleration sensor is used as sensor 200, a state
of vibration of agitation vessel 150 is able to be sensed by
directly measuring an acceleration of medium 20 during vibration.
For example, GH313A or GH613 (each of which is manufactured by
Keyence Corporation) as a sensor head and GA-245 (manufactured by
Keyence Corporation) as an amplifier unit can be adopted for the
acceleration sensor.
[0114] An acceleration of medium 20 is preferably not lower than
about 2.5 G and not higher than about 20.0 G, for example. When the
acceleration of medium 20 is lower than about 2.5 G, sufficient
energy for rolling a metal contained in the baked electrode layer
cannot be obtained. When the acceleration of medium 20 is higher
than about 20.0 G, damage to the multilayer body is great.
[0115] When a laser displacement sensor is used as sensor 200, a
state of vibration of agitation vessel 150 is able to be sensed by
measuring an amount of movement of agitation vessel 150 by emitting
laser beams to agitation vessel 150.
[0116] By thus measuring an acceleration of medium 20 or an amount
of movement of agitation vessel 150, a state of vibration of
agitation vessel 150, more specifically a frequency of agitation
vessel 150, is able to be sensed.
[0117] Drive motor controller 210 controls an operation of drive
motor 160 based on a result of sensing by sensor 200.
[0118] FIG. 10 is a flowchart showing details of the step of
surface treatment of the baked electrode layer shown in FIG. 5.
Details of step S12 of surface treatment of the baked electrode
layer will be described with reference to FIG. 10.
[0119] As shown in FIG. 10, in step S12 of surface treatment of the
baked electrode layer, initially, in a step S121, a plurality of
multilayer bodies 12 and media (not shown in FIG. 10) are
introduced into agitation vessel 150, the plurality of multilayer
bodies 12 each including first end surface 12e and second end
surface 12f opposed to each other, first side surface 12c and
second side surface 12d opposed to each other, and first main
surface 12a and second main surface 12b opposed to each other,
first end surface 12e being provided with first baked electrode
layer 15a, and second end surface 12f being provided with second
baked electrode layer 16a.
[0120] Medium 20 is spherical. A diameter of medium 20 is
preferably smaller than a diagonal of first end surface 12e and
second end surface 12f. With such a diameter, medium 20 and the
multilayer body can readily be separated from each other by using a
meshed sieve.
[0121] For example, tungsten or zirconium can be used as a material
for medium 20. Medium 20 may contain tungsten or zirconium.
Cemented carbide containing cobalt and/or chromium and tungsten may
be used as a material for medium 20. Medium 20 may further contain
cobalt and/or chromium in addition to tungsten.
[0122] Reforming energy for reforming first baked electrode layer
15a and the second baked electrode layer by having media 20 collide
against first baked electrode layer 15a and second baked electrode
layer 16a provided in multilayer body 12 as will be described later
can be expressed as a product of collision energy and a frequency
of collision.
[0123] Higher reforming energy is obtained by extending a time
period (a process time period) for applying vibration to multilayer
bodies 12 and media 20 as will be described later. Collision energy
(kinetic energy), however, is in proportion to a mass of media 20,
and hence the process time period can be reduced by increasing a
mass of media 20.
[0124] Since tungsten is higher in specific gravity than zirconium,
by using tungsten as medium 20, a mass can be increased as compared
with an example of using zirconium even though the diameter is the
same. The process time period can thus be reduced.
[0125] Medium 20 has a diameter preferably not smaller than about
0.2 mm and not greater than about 2.0 mm and preferably not smaller
than about 0.4 mm and not greater than about 1.0 mm.
[0126] When medium 20 has too small a diameter, kinetic energy of
medium 20 is low and a metal exposed at the surface layer of the
baked electrode layer cannot sufficiently be rolled. When a
diameter is too large, kinetic energy of medium 20 is high and
multilayer body 12 is damaged.
[0127] Medium 20 preferably has a smooth surface and has surface
roughness Sa preferably not greater than 200 nm and more preferably
not greater than 190 nm.
[0128] Medium 20 has a specific gravity preferably not lower than 5
and not higher than 18. When a specific gravity is too low, kinetic
energy of medium 20 is low and a metal exposed at the surface layer
of the baked electrode layer cannot sufficiently be rolled. When a
specific gravity is too high, the multilayer body is damaged.
[0129] Medium 20 has a Vickers hardness preferably not lower than
1000 HV and not higher than 2500 HV. When the hardness is too low,
medium 20 will break. When the hardness is too high, the multilayer
body is damaged.
[0130] A total of volumes of a plurality of multilayer bodies 12
introduced into agitation vessel 150 is preferably at most 1/2 and
further preferably at most 1/3 of the total of volumes of media 20
introduced into agitation vessel 150. When an amount of the
plurality of multilayer bodies 12 with respect to media 20 is
excessively large, workability by media 20 becomes poor and hence a
crack may be produced in a corner portion of multilayer body 12 or
multilayer body 12 may be chipped or broken.
[0131] In a step S122, vibration energy is applied to the plurality
of multilayer bodies 12 and media 20 by causing agitation vessel
150 to vibrate. Specifically, agitation vessel 150 is caused to
vibrate by surface treatment apparatus 100.
[0132] FIG. 11 is a diagram showing the step of applying vibration
energy to the plurality of multilayer bodies and media 20 in the
step of applying vibration to the agitation vessel shown in FIG.
10. As shown in FIG. 11, by rotating eccentric load 170 in surface
treatment apparatus 100, positions of the centers of gravity of
drive motor 160 and vibration reception plate 140 are displaced
from each other. Thus, vibration reception plate 140 is inclined
and extension and contraction of the plurality of elastic members
180 becomes uneven. As vibration reception plate 140 is inclined, a
central axis C of bottom portion 151 of agitation vessel 150 is
also inclined.
[0133] As a position of eccentric load 170 is continuously varied
with rotation, inclination of vibration reception plate 140 is
varied in accordance with a position of eccentric load 170.
Consequently, a position where unevenness in extension and
contraction of elastic member 180 is significant also moves in the
circumferential direction. As the plurality of elastic members 180
thus extend and contract, vibration propagates from the plurality
of elastic members 180 to agitation vessel 150 such that a
direction of inclination of central axis C of bottom portion 151 is
continuously varied.
[0134] With continuous variation also in the direction of
inclination of central axis C of bottom portion 151, when an
annular virtual axis VL circumferentially surrounding central axis
C of bottom portion 151 before agitation vessel 150 vibrates is
assumed, vibration is applied to multilayer bodies 12 and media 20
such that multilayer bodies 12 and media 20 follow a helical trace
which helically surrounds virtual axis VL along an axial direction
of virtual axis VL.
[0135] As vibration of agitation vessel 150 is transmitted to the
plurality of multilayer bodies and media 20 introduced into
agitation vessel 150, the plurality of multilayer bodies and media
20 are agitated while they are helically tumbled. Media 20 thus
roll the surface layer of the baked electrode layer while they
collide against the baked electrode layer to thus reduce glass
contained in the surface layer of the baked electrode layer.
Consequently, a state of the surface layer of the baked electrode
layer is reformed and second region 15a2 described above which is
high in density of a metal and has a smooth surface is formed.
[0136] Agitation vessel 150 itself does not rotate around central
axis C although the direction of inclination of agitation vessel
150 is varied in the circumferential direction. Therefore, even
when a multilayer body comes in contact with agitation vessel 150,
excessive force will not be applied from agitation vessel 150 to
the multilayer body. Therefore, fracture and chipping of the
multilayer body are able to be significantly reduced or
prevented.
[0137] In agitation vessel 150, as a distance from shaft portion
155 is greater in the radial direction, more vibration is
transmitted to the multilayer bodies and media 20 introduced in
agitation vessel 150. Since bottom portion 151 is inclined and
shaft portion 155 is also inclined, vibration is more likely to be
received from proximate elastic member 180 as shaft portion 155 is
more proximate to any of the plurality of elastic members 180.
[0138] Therefore, by providing a structure that ensures that the
plurality of multilayer bodies and media 20 stay at a position
radially distant from shaft portion 155 in agitation vessel 150,
vibration is able to effectively be transmitted to the plurality of
multilayer bodies and media 20. Surface treatment of the baked
electrode layer is thus more efficient.
[0139] Agitation vessel 150 is preferably caused to vibrate such
that a frequency of agitation vessel 150 resonates with a natural
frequency of agitation vessel 150. The natural frequency refers to
a frequency at which vibration intensity is higher, that is, energy
of working is higher. Surface treatment of the baked electrode
layer is able to be efficient by causing agitation vessel 150 to
vibrate such that a frequency of agitation vessel 150 is set to the
natural frequency.
[0140] A frequency of agitation vessel 150 is able to be adjusted,
for example, by changing a speed of rotation of eccentric load 170
by drive motor 160. For such adjustment, sensor 200 senses a state
of vibration of agitation vessel 150.
[0141] When sensor 200 senses deviation of the frequency of
agitation vessel 150 from the natural frequency, drive motor
controller 210 controls an operation of drive motor 160 such that a
frequency of agitation vessel 150 is close to the natural frequency
of agitation vessel 150.
[0142] With reference again to FIG. 5, in a step S13, multilayer
body 12 with the baked electrode layer having second region 15a2
formed thereon is plated. Ni plating and Sn plating are
successively provided on the baked electrode layer so that plating
layer 15b and plating layer 16b as well as plating layer 15c and
plating layer 16c are formed. First external electrode 15 and
second external electrode 16 are thus formed on the outer surface
of multilayer body 12.
[0143] Multilayer ceramic capacitor 10 can be manufactured through
the series of steps described above.
[0144] As set forth above, the method of manufacturing a multilayer
ceramic capacitor according to the first preferred embodiment
includes introducing a plurality of multilayer bodies and media 20
into a container, each of the plurality of multilayer bodies
including first end surface 12e and second end surface 12f opposed
to each other, first side surface 12c and second side surface 12d
opposed to each other, and first main surface 12a and second main
surface 12b opposed to each other, first end surface 12e being
provided with first baked electrode layer 15a, and second end
surface 12f being provided with second baked electrode layer 16a,
and applying vibration energy to the plurality of multilayer bodies
12 and media 20 by causing agitation vessel 150 to vibrate.
[0145] In applying vibration to the plurality of multilayer bodies
12 and media 20, vibration is applied to multilayer bodies 12 and
media 20 such that multilayer bodies 12 and media 20 follow a
helical trace which helically surrounds virtual axis VL along the
axial direction of virtual axis VL described above by causing
agitation vessel 150 to vibrate. Thus, in the present preferred
embodiment, agitation vessel 150 does not rotate around central
axis C of the bottom portion as compared with sandblasting in which
a barrel is rotated around an axis while abrasive powders are blown
toward multilayer bodies. Therefore, even when the plurality of
multilayer bodies 12 come in contact with agitation vessel 150,
application of excessive force from agitation vessel 150 to the
multilayer bodies is able to be significantly reduced or prevented.
Consequently, fracture and chipping of a multilayer body are able
to be significantly reduced or prevented.
[0146] By applying vibration energy to the plurality of multilayer
bodies 12 and media 20, the surface layer of the baked electrode
layer is polished while media 20 are rubbed against the surface
layer of first baked electrode layer 15a and second baked electrode
layer 16a by agitating the multilayer bodies each provided with
first baked electrode layer 15a and second baked electrode layer
16a and media 20.
[0147] Thus, glass contained in the surface layer of first baked
electrode layer 15a and second baked electrode layer 16a is
reduced, a metal contained in first baked electrode layer 15a and
second baked electrode layer 16a is rolled, and the surface layer
of first baked electrode layer 15a and second baked electrode layer
16a is planarized. Consequently, the surfaces of first baked
electrode layer 15a and second baked electrode layer 16a are
smoothened, density of a metal on the side of the surface layer of
first baked electrode layer 15a and second baked electrode layer
16a can be high, and the surfaces of first baked electrode layer
15a and second baked electrode layer 16a are able to be
reformed.
[0148] By using tungsten which is spherical in shape and higher in
specific gravity than zirconium as medium 20, a mass and kinetic
energy of medium 20 is able to be increased as described above. A
time period (process time period) required for surface treatment of
first baked electrode layer 15a and second baked electrode layer
16a is thus able to be reduced.
[0149] By setting a diameter of medium 20 to be not smaller than
about 0.2 mm and not greater than about 2.0 mm, medium 20 is able
to collide against a multilayer body with suitable kinetic energy
and a metal exposed at the surface layer of first baked electrode
layer 15a and the surface layer of second baked electrode layer 16a
is able to be sufficiently be rolled without damaging multilayer
body 12. Consequently, the surface of the baked electrode layer
provided in an electronic component body (multilayer body) is able
to be reformed.
Second Preferred Embodiment
[0150] FIG. 12 is a partial cross-sectional view showing details of
a baked electrode layer of a multilayer ceramic capacitor
manufactured in accordance with a method of manufacturing a
multilayer ceramic capacitor according to a second preferred
embodiment of the present invention. A multilayer ceramic capacitor
10A manufactured in accordance with the method of manufacturing a
multilayer ceramic capacitor according to the second preferred
embodiment will be described with reference to FIG. 12.
[0151] As shown in FIG. 12, multilayer ceramic capacitor 10A
according to the second preferred embodiment is different from
multilayer ceramic capacitor 10 according to the first preferred
embodiment in the structure of a first baked electrode layer 15aA
and a second baked electrode layer (not shown). The construction is
otherwise substantially the same. Since the second baked electrode
layer is similar in construction to first baked electrode layer
15aA, description thereof will not be provided.
[0152] First baked electrode layer 15aA is constructed such that
second region 15a2 is in contact with a corner portion of
multilayer body 12. By way of example, only second region 15a2 of
first baked electrode layer 15aA is provided on a corner portion C1
which connects first main surface 12a of multilayer body 12 and
first end surface 12e of multilayer body 12 to each other. Corner
portion C1 refers to a curved portion located on an inner side of a
first virtual line VL1 which passes through a ridgeline portion
where first main surface 12a and first side surface 12c intersect
with each other and a second virtual line VL2 which passes through
a ridgeline portion where first end surface 12e and first side
surface 12c intersect with each other when viewed in the direction
of width W.
[0153] On a side of first end surface 12e on first main surface 12a
of multilayer body 12, first region 15a1 and second region 15a2 of
first baked electrode layer 15aA are successively provided from the
side of multilayer body 12. Though not shown in FIG. 12, similarly,
on the side of first end surface 12e on second main surface 12b of
multilayer body 12, first region 15a1 and second region 15a2 of
first baked electrode layer 15aA are successively provided from the
side of multilayer body 12. On first end surface 12e of multilayer
body 12, first region 15a1 and second region 15a2 of first baked
electrode layer 15aA are provided from the side of multilayer body
12.
[0154] First baked electrode layer 15aA is formed preferably by
applying a conductive paste containing glass and a metal to first
end surface 12e by immersion and baking the conductive paste after
it is dried. In application of the conductive paste to first end
surface 12e, it tends to be small in thickness in a corner
portion.
[0155] Therefore, the baked electrode layer formed when the
conductive paste applied to first end surface 12e is baked is also
small in thickness in the corner portion. When the baked electrode
layer formed in the corner portion is small in thickness to a
considerable extent, it is rolled by medium 20 in surface treatment
thereof so that only second region 15a2 which is high in density of
the metal and has a smooth surface is formed.
[0156] A baked electrode layer located in a portion other than the
corner portion is greater in thickness than the baked electrode
layer located in the corner portion. Therefore, in surface
treatment of the baked electrode layer, second region 15a2 which is
high in density of the metal and has a smooth surface is provided
only on the side of the surface layer and first region 15a1 where
pores and glass remain is provided on the side of multilayer body
12.
[0157] In particular, when a small multilayer body of which length
dimension is not greater than about 1.6 mm, width dimension is not
greater than about 0.8 mm, and thickness dimension is not greater
than about 0.8 mm is handled, a metal in the baked electrode layer
in the corner portion tends to be rolled in surface treatment as
described above and the construction of multilayer ceramic
capacitor 10A as in the second preferred embodiment tends to be
obtained.
[0158] According to the construction as above, second region 15a2
high in density of the metal is provided on the side of the surface
layer of the first baked electrode layer and the second baked
electrode layer so that moisture resistance of multilayer body 12
is able to be improved.
[0159] As the surface of second region 15a2 is constructed to be
smooth, a defect in plating layer 15b and plating layer 15c are
able to be significantly reduced or prevented in formation of
plating layer 15b and plating layer 15c. Continuity between plating
layer 15b and plating layer 15c is able to be improved.
[0160] As first region 15a1 contains pores, first baked electrode
layer 15aA has cushioning properties in a portion other than the
corner portion and external impacts applied to multilayer ceramic
capacitor 10A are able to be absorbed.
[0161] A method of manufacturing multilayer ceramic capacitor 10A
according to the second preferred embodiment is similar to the
method of manufacturing multilayer ceramic capacitor 10 according
to the first preferred embodiment.
[0162] In manufacturing multilayer ceramic capacitor 10A in
accordance with the method of manufacturing multilayer ceramic
capacitor 10A according to the second preferred embodiment,
processing substantially the same as in steps S1 to S8 according to
the first preferred embodiment is performed.
[0163] Then, in a step in conformity with step S9 according to the
first preferred embodiment, a conductive paste is applied to a side
of first end surface 12e and a side of second end surface 12f such
that a thickness of the conductive paste in a corner portion of
multilayer body 12 is smaller than a thickness of the conductive
paste applied to a portion of first main surface 12a and second
main surface 12b, a part of first side surface 12c and second side
surface 12d, and first end surface 12e and second end surface
12f.
[0164] A plurality of multilayer bodies each provided with the
first baked electrode layer and the second baked electrode layer
constructed such that a portion thereof corresponding to a corner
portion of multilayer body 12 is smaller in thickness than other
portions are formed (prepared) by performing processing
substantially the same as in steps S10 and S11 according to the
first preferred embodiment.
[0165] Then, in a step in conformity with step S12 according to the
first preferred embodiment, the plurality of multilayer bodies and
media 20 are introduced into agitation vessel 150. Vibration energy
is applied to the plurality of multilayer bodies 12 and media 20 by
causing agitation vessel 150 to vibrate. In applying vibration
energy to the plurality of multilayer bodies 12 and media 20,
second region 15a2 which is high in density of a metal and has a
smooth surface and first region 15a1 containing glass and pores are
formed in the baked electrode layer. In a portion of the baked
electrode layer corresponding to the corner portion of multilayer
body 12, second region 15a2 is formed so as to contact with the
corner portion of multilayer body 12, and in portions other than
that, first region 15a1 is provided on the side of multilayer body
12 and second region 15a2 is formed to cover first region 15a1.
[0166] Processing substantially the same as in step S13 according
to the first preferred embodiment is then performed. Through the
steps as above, multilayer ceramic capacitor 10A according to the
second preferred embodiment is manufactured.
[0167] As set forth above, the method of manufacturing multilayer
ceramic capacitor 10A according to the second preferred embodiment
also achieves an effect substantially the same as in the method of
manufacturing multilayer ceramic capacitor 10 according to the
first preferred embodiment.
Third Preferred Embodiment
[0168] FIG. 13 is a cross-sectional view of a multilayer ceramic
capacitor manufactured in accordance with a method of manufacturing
a multilayer ceramic capacitor according to a third preferred
embodiment of the present invention. A multilayer ceramic capacitor
10B manufactured with the method of manufacturing a multilayer
ceramic capacitor according to the third preferred embodiment will
be described with reference to FIG. 13.
[0169] As shown in FIG. 13, multilayer ceramic capacitor 10B
according to the third preferred embodiment is different from
multilayer ceramic capacitor 10 according to the first preferred
embodiment in construction of a first external electrode 15B and a
second external electrode 16B. The construction is otherwise
substantially the same.
[0170] A first external electrode 15B includes first baked
electrode layer 15a, a resin layer 15d, and plating layer 15b and
plating layer 15c sequentially from the side of multilayer body 12.
First baked electrode layer 15a and resin layer 15d define and
function as an underlying electrode. Resin layer 15d is provided
between first baked electrode layer 15a and plating layer 15b.
[0171] A second external electrode 16B includes second baked
electrode layer 16a, a resin layer 16d, and plating layer 16b and
plating layer 16c sequentially from the side of multilayer body 12.
Second baked electrode layer 16a and resin layer 16d function as an
underlying electrode. Resin layer 16d is provided between second
baked electrode layer 16a and plating layer 16b.
[0172] Resin layer 15d and resin layer 16d contain conductive
particles and a thermosetting resin. Particles of a metal such as
Cu or Ag can be used as conductive particles. For example, a phenol
resin, an acrylic resin, a silicone resin, an epoxy resin, and a
polyimide resin can be used as a thermosetting resin.
[0173] Resin layer 15d and resin layer 16d may include a plurality
of stacked layers. Resin layer 15d and resin layer 16d have a
thickness preferably not smaller than about 10 .mu.m and not
greater than about 90 .mu.m, for example.
[0174] Resin layer 15d and resin layer 16d have continuity not
lower than about 80% and not higher than about 90% on a corner
portion of multilayer body 12, for example. This continuity can be
confirmed in observation with an SEM after multilayer ceramic
capacitor 10B is polished. In polishing, for example, multilayer
ceramic capacitor 10B is polished to a position in the center in
the direction of width W so as to expose a cross-section
perpendicular or substantially perpendicular to direction of width
W.
[0175] According to the construction as above, second region 15a2
high in density of a metal is provided on the side of the surface
layer in the first baked electrode layer and the second baked
electrode layer so that moisture resistance of multilayer body 12
is improved.
[0176] As first region 15a1 contains pores, first baked electrode
layer 15a has cushioning properties in a portion other than the
corner portion and external impacts applied to multilayer ceramic
capacitor 10B are able to be absorbed.
[0177] As the surface of second region 15a2 is constructed to be
smooth, delamination tends to occur in a boundary portion between
first baked electrode layer 15a and resin layer 15d and a boundary
portion between second baked electrode layer 16a and resin layer
16d on a side of an end portion of a fold-back portion of first
external electrode 15B and second external electrode 16B.
[0178] As a mount substrate is warped when multilayer ceramic
capacitor 10 is mounted on a mount substrate, an external force may
be applied to multilayer ceramic capacitor 10B. Such external force
tends to be concentrated on the side of the end portion of the
fold-back portion of first external electrode 15B and second
external electrode 16B. When an external force is concentrated to
the end portion of the fold-back portion, delamination occurs in
the boundary portion between first baked electrode layer 15a and
resin layer 15d and the boundary portion between second baked
electrode layer 16a and resin layer 16d so that stress applied to
multilayer body 12 is relaxed. Consequently, multilayer body 12 is
prevented from breaking.
[0179] FIG. 14 is a flowchart showing a method of manufacturing a
multilayer ceramic capacitor according to the third preferred
embodiment. The method of manufacturing a multilayer ceramic
capacitor according to the third preferred embodiment will be
described with reference to FIG. 14.
[0180] As shown in FIG. 14, in manufacturing multilayer ceramic
capacitor 10B according to the method of manufacturing multilayer
ceramic capacitor 10B according to the third preferred embodiment,
processing substantially the same as in the first preferred
embodiment is performed in steps S1 to S12.
[0181] In a step S13A, a thermosetting resin containing conductive
particles is applied onto first baked electrode layer 15a and
second baked electrode layer 16a and cured by being heated.
Conductive resin layers 15d and 16d are thus formed.
[0182] In a step S13B, processing substantially the same as in step
S13 according to the first preferred embodiment is performed to
form plating layer 15b and plating layer 15c on resin layer 15d and
to form plating layer 16b and plating layer 16c on resin layer
16d.
[0183] Through the steps as above, multilayer ceramic capacitor 10B
according to the third preferred embodiment can be
manufactured.
[0184] As set forth above, the method of manufacturing multilayer
ceramic capacitor 10B according to the third preferred embodiment
also achieves an effect substantially the same as in the method of
manufacturing multilayer ceramic capacitor 10 according to the
first preferred embodiment.
First Verification Experiment
[0185] FIG. 15 is a diagram showing a condition and a result in a
first verification experiment conducted for verifying advantageous
effects of the preferred embodiments of the present invention. The
first verification experiment conducted in order to verify the
effect of the preferred embodiments will be described with
reference to FIG. 15.
[0186] As shown in FIG. 15, in conducting the first verification
experiment, a plurality of multilayer bodies 12 according to
Examples 1 and 2 and Comparative Examples 1 to 7 each provided with
first baked electrode layer 15a on the side of first end surface
12e and provided with second baked electrode layer 16a on the side
of second end surface 12f of multilayer body 12 were prepared. In a
stage of preparation, first baked electrode layer 15a and second
baked electrode layer 16a have not yet been subjected to surface
treatment.
[0187] Each multilayer body 12 had a length dimension of 1.0 mm, a
width dimension of 0.5 mm, and a height dimension of 0.5 mm.
[0188] In Examples 1 and 2 and Comparative Examples 1 to 7, a
medium which was spherical and composed of tungsten was used as
medium 20 to be used in the surface treatment. Medium 20 had a
diameter of 0.5 mm.
[0189] The prepared multilayer bodies according to Examples 1 and 2
and Comparative Examples 1 to 7 were subjected to surface treatment
of the baked electrode layer with surface treatment apparatus 100
described above and whether or not a crack was generated and
whether or not the surface of the baked electrode layer was
reformed was checked.
[0190] In Comparative Example 1, a total of volumes of the
plurality of multilayer bodies introduced into agitation vessel 150
was set to 1/2 of the total of volumes of media 20 introduced into
agitation vessel 150. A process time period was set to seven hours
and a frequency of agitation vessel 150 was set to 15 Hz lower than
the natural frequency of agitation vessel 150.
[0191] In this case, though no crack was generated in the
multilayer bodies after surface treatment, a state of the surface
was not improved. Second region 15a2 could not sufficiently be
formed.
[0192] In Comparative Example 2, a total of volumes of the
plurality of multilayer bodies introduced into agitation vessel 150
was set to 1/2 of the total of volumes of media 20 introduced into
agitation vessel 150. A process time period was set to seven hours
and a frequency of agitation vessel 150 was set to 35 Hz higher
than the natural frequency of agitation vessel 150.
[0193] In this case, though no crack was generated in the
multilayer bodies after surface treatment, a state of the surface
was not improved. Second region 15a2 could not sufficiently be
formed.
[0194] In Comparative Example 3, a total of volumes of the
plurality of multilayer bodies introduced into agitation vessel 150
was set to 6/10 of the total of volumes of media 20 introduced into
agitation vessel 150. A process time period was set to three hours
and a frequency of agitation vessel 150 was set to 23 Hz as high as
the natural frequency of agitation vessel 150.
[0195] In this case, after surface treatment, a crack was generated
in four of 100 multilayer bodies. A state of the surface was not
improved and second region 15a2 could not sufficiently be
formed.
[0196] In Comparative Example 4, a total of volumes of the
plurality of multilayer bodies introduced into agitation vessel 150
was set to 6/10 of the total of volumes of media 20 introduced into
agitation vessel 150. A process time period was set to five hours
and a frequency of agitation vessel 150 was set to 23 Hz as high as
the natural frequency of agitation vessel 150.
[0197] In this case, after surface treatment, a crack was generated
in six of 100 multilayer bodies. A state of the surface was not
improved and second region 15a2 could not sufficiently be
formed.
[0198] In Comparative Example 5, a total of volumes of the
plurality of multilayer bodies introduced into agitation vessel 150
was set to 8/10 of the total of volumes of media 20 introduced into
agitation vessel 150. A process time period was set to five hours
and a frequency of agitation vessel 150 was set to 23 Hz as high as
the natural frequency of agitation vessel 150.
[0199] In this case, after surface treatment, a crack was generated
in 35 of 100 multilayer bodies. A state of the surface was not
improved and second region 15a2 could not sufficiently be
formed.
[0200] In Comparative Example 6, a total of volumes of the
plurality of multilayer bodies introduced into agitation vessel 150
was set to be equal to the total of volumes of media 20 introduced
into agitation vessel 150. A process time period was set to five
hours and a frequency of agitation vessel 150 was set to 23 Hz as
high as the natural frequency of agitation vessel 150.
[0201] In this case, after surface treatment, a crack was generated
in 41 of 100 multilayer bodies. A state of the surface was not
improved and second region 15a2 could not sufficiently be
formed.
[0202] In Comparative Example 7, a total of volumes of the
plurality of multilayer bodies introduced into agitation vessel 150
was set to be equal to the total of volumes of media 20 introduced
into agitation vessel 150. A process time period was set to seven
hours and a frequency of agitation vessel 150 was set to 23 Hz as
high as the natural frequency of agitation vessel 150.
[0203] In this case, after surface treatment, a crack was generated
in 58 of 100 multilayer bodies. A state of the surface was not
improved and second region 15a2 could not sufficiently be
formed.
[0204] In Example 2, a total of volumes of the plurality of
multilayer bodies introduced into agitation vessel 150 was set to
at most 1/3 (3/10) of the total of volumes of media 20 introduced
into agitation vessel 150. A process time period was set to five
hours and a frequency of agitation vessel 150 was set to 23 Hz as
high as the natural frequency of agitation vessel 150.
[0205] In this case, after surface treatment, no crack was
generated in the multilayer bodies and a state of the surface was
improved. Second region 15a2 could sufficiently be formed in the
surface layer of the baked electrode layer.
[0206] In Example 1, a total of volumes of the plurality of
multilayer bodies introduced into agitation vessel 150 was set to
1/2 of the total of volumes of media 20 introduced into agitation
vessel 150. A process time period was set to five hours and a
frequency of agitation vessel 150 was set to 23 Hz as high as the
natural frequency of agitation vessel 150.
[0207] In this case, after surface treatment, no crack was
generated in the multilayer bodies and a state of the surface was
improved. Second region 15a2 could sufficiently be formed in the
surface layer of the baked electrode layer.
[0208] As set forth above, it can be concluded as shown in the
results in Examples 1 and 2 that the surface of the baked electrode
layer provided in the multilayer body can be reformed while
fracture and chipping of the multilayer body is suppressed by using
the method of manufacturing a multilayer ceramic capacitor
according to the present preferred embodiment. The surface of the
baked electrode layer provided in the multilayer body is able to be
reformed while fracture and chipping of the multilayer body is
significantly reduced or prevented.
[0209] It was confirmed that workability by media 20 could be good
and generation of a crack in a corner portion of multilayer body 12
or chipping or fracture of multilayer body 12 could be prevented by
setting a total of volumes of the plurality of multilayer bodies 12
introduced into agitation vessel 150 to at most 1/2 of the total of
volumes of media 20 introduced into agitation vessel 150 in surface
treatment. Furthermore, it was confirmed that a good state of the
surface was obtained by setting a total of volumes of the plurality
of multilayer bodies 12 introduced into agitation vessel 150 to at
most 1/3 of the total of volumes of media 20 introduced into
agitation vessel 150.
[0210] Based on comparison between Examples 1 and 2 and Comparative
Examples 1 and 2, by setting a frequency of agitation vessel 150 to
a natural frequency of agitation vessel 150, generation of a crack
in a corner portion of multilayer body 12 or chipping or fracture
of multilayer body 12 is prevented and the surface of the baked
electrode layer is able to be reformed even though a process time
period is shorter. It can thus be concluded that vibration can
effectively be transmitted to the plurality of multilayer bodies
and media 20 and surface treatment is able to be efficient by
setting a frequency of agitation vessel 150 to a natural frequency
of agitation vessel 150.
[0211] In the first verification experiment, in Example 2, a state
of the baked electrode layer before and after surface treatment was
observed with a scanning electron microscope. FIGS. 16 to 22 below
show results of observation of the side of the first end surface,
that is, the side of the first baked electrode layer.
[0212] FIG. 16 is a diagram showing a state of the surface of the
baked electrode layer before surface treatment in Example 2 shown
in FIG. 15. FIG. 17 is a diagram showing a state of the surface of
the baked electrode layer after surface treatment in Example 2
shown in FIG. 15. FIG. 17 shows a state midway through the surface
treatment, after lapse of one hour of the process time period. A
state of the surface of the baked electrode layer before and after
surface treatment will be described with reference to FIGS. 16 and
17.
[0213] As shown in FIG. 16, pores to a considerable extent were
provided in the surface of the baked electrode layer before surface
treatment. A porosity of the surface of the baked electrode layer
before surface treatment was approximately 2.5%.
[0214] As shown in FIG. 17, substantially no pore was provided in
the surface of the baked electrode layer after surface treatment. A
porosity of the surface of the baked electrode layer after surface
treatment was approximately 0.3%. In a stage midway through surface
treatment as well, by performing surface treatment, density of a
metal was high in the baked electrode layer and the surface of the
baked electrode layer was smoothened. The surface of the baked
electrode layer was reformed by surface treatment.
[0215] FIG. 18 is a diagram showing a state of the surface of the
baked electrode layer after surface treatment with the use of
medium 20 composed of zirconia as a reference example. In the
reference example, conditions except for medium 20 are the same as
in Example 2. FIG. 18 also shows a state midway through surface
treatment, after lapse of one hour of the process time period. A
state of the surface of the baked electrode layer after surface
treatment with the medium composed of zirconia being used as medium
20 will be described with reference to FIG. 18.
[0216] As shown in FIG. 18, in the reference example, pores
remained although the number thereof is small. A porosity of the
surface of the baked electrode layer after surface treatment was
approximately 1.0%. In a stage midway through surface treatment as
well, by thus performing surface treatment, density of the metal in
the baked electrode layer was high and the surface of the baked
electrode layer was smoothened. In the reference example as well,
the surface of the baked electrode layer was reformed by surface
treatment.
[0217] It can be seen based on comparison between FIG. 17 in which
a medium composed of tungsten was used as medium 20 and FIG. 18 in
which a medium composed of zirconia was used as medium 20 that, by
using the medium composed of tungsten as medium 20, a rate of
reformation of the surface was higher even though the process time
period was the same. It could be confirmed that the process time
period could be shortened by increasing a mass of medium 20.
[0218] FIG. 19 is a cross-sectional view showing a state of the
baked electrode layer in the vicinity of a corner portion before
surface treatment in Example 2 shown in FIG. 15. FIG. 20 is a
cross-sectional view showing a state of the baked electrode layer
in the vicinity of the corner portion after surface treatment in
Example 2 shown in FIG. 15. A state of the baked electrode layer in
the vicinity of the corner portion before and after surface
treatment will be described with reference to FIGS. 19 and 20.
[0219] As shown in FIG. 19, the baked electrode layer in the
vicinity of the corner portion before surface treatment contained
pores to a considerable extent from the side of multilayer body 12
toward the surface layer of the baked electrode layer and contained
glass to a considerable extent. The baked electrode layer was in a
state of first region 15a1 described above throughout the direction
of thickness. Therefore, the surface of the baked electrode layer
was rough.
[0220] As shown in FIG. 20, in the baked electrode layer in the
vicinity of the corner portion after surface treatment, density of
the metal was high over a range of approximately 10 .mu.m to
approximately 15 .mu.m, for example, in the direction of depth from
the side of the surface layer of the baked electrode layer and the
surface of the baked electrode layer was smoothened. Specifically,
after surface treatment, on the corner portion, second region 15a2
described above which was high in density of the metal and had a
smooth surface was formed on multilayer body 12. In a portion
distant from the corner portion, first region 15a1 was formed on
multilayer body 12 and second region 15a2 was formed on first
region 15a1.
[0221] FIG. 21 is a cross-sectional view showing a state of the
baked electrode layer in a central portion of the end surface
before surface treatment in Example 2 shown in FIG. 15. FIG. 22 is
a cross-sectional view showing a state of the baked electrode layer
in the central portion of the end surface after surface treatment
in Example 2 shown in FIG. 15. A state of the baked electrode layer
in the central portion of the end surface before and after surface
treatment will be described with reference to FIGS. 21 and 22.
[0222] As shown in FIG. 21, the baked electrode layer in the
central portion of the end surface before surface treatment
contained pores to a considerable extent from the side of
multilayer body 12 toward the surface layer of the baked electrode
layer and contained glass to a considerable extent. The baked
electrode layer was in a state of first region 15a1 described above
throughout the direction of thickness. Therefore, the surface of
the baked electrode layer was rough.
[0223] As shown in FIG. 22, in the baked electrode layer in the
central portion of the end surface after surface treatment, density
of the metal was high over a range of approximately 10 .mu.m to
approximately 15 .mu.m, for example, in the direction of depth from
the side of the surface layer of the baked electrode layer and the
surface of the baked electrode layer was smoothened. Specifically,
after surface treatment, in the central portion of the end surface,
first region 15a1 was formed on multilayer body 12 and second
region 15a2 was formed on first region 15a1.
[0224] It could be confirmed in FIGS. 19 to 22 that a state was
reformed by surface treatment not only in the surface of the baked
electrode layer but also in the direction of depth. It was
confirmed that the baked electrode layer was uniformly reformed
through the surface treatment since a depth of a portion where the
baked electrode layer was reformed in the vicinity of the corner
portion and a depth of a portion where the baked electrode layer
was reformed in the central portion of the end surface were
substantially equal to each other.
[0225] Furthermore, in the first verification experiment, twenty
four multilayer ceramic capacitors according to Comparative Example
8 and twenty four multilayer ceramic capacitors according to
Example 2 were prepared and subjected to a moisture resistance load
test. A multilayer ceramic capacitor having a plating layer formed
on a baked electrode layer without surface treatment of the baked
electrode layer was prepared as the multilayer ceramic capacitor
according to Comparative Example 8. A multilayer ceramic capacitor
having a plating layer formed on a baked electrode layer subjected
to surface treatment under conditions according to Example 2
described above was prepared as the multilayer ceramic capacitor
according to Example 2.
[0226] The multilayer ceramic capacitors according to Comparative
Example 8 and the multilayer ceramic capacitors according to
Example 2 were exposed to an environment at 125.degree. C. and a
humidity of 95% for forty hours and variation in resistance was
determined.
[0227] In Comparative Example 8, six of twenty four multilayer
ceramic capacitors were deteriorated.
[0228] In Example 2, only one multilayer ceramic capacitor of
twenty four multilayer ceramic capacitors was deteriorated and
moisture resistance was improved as compared with Comparative
Example 8.
[0229] It was confirmed from the foregoing that entry of water
vapor could be suppressed and thus reliability of the multilayer
ceramic capacitor could be improved by subjecting the baked
electrode layer to surface treatment to thereby form a metal layer
(second region) high in density.
Second Verification Experiment
[0230] FIG. 23 is a diagram showing a condition and a result of a
second verification experiment conducted for verifying advantageous
effects of the preferred embodiments of the present invention. The
second verification experiment conducted for verifying advantageous
effects of the preferred embodiments will be described with
reference to FIG. 23. FIG. 23 shows surface roughness Sa (nm) of
the baked electrode layer after surface treatment of the baked
electrode layer with a diameter and a specific gravity of the
medium being set as shown in the figure.
[0231] In conducting the second verification experiment, a
plurality of multilayer bodies 12 each provided with first baked
electrode layer 15a on the side of first end surface 12e and
provided with second baked electrode layer 16a on the side of
second end surface 12f of multilayer body 12 were prepared. In a
stage of preparation, first baked electrode layer 15a and second
baked electrode layer 16a have not yet been subjected to surface
treatment.
[0232] Multilayer body 12 had a length dimension of 1.0 mm, a width
dimension of 0.5 mm, and a height dimension of 0.5 mm.
[0233] As shown in FIG. 23, media different in specific gravity and
diameter from one another were prepared as media 20 used in surface
treatment of the plurality of multilayer bodies. Specifically,
various media having a diameter of 0.1 mm, 0.2 mm, 0.4 mm, 1.0 mm,
2.0 mm, or 2.5 mm and having a specific gravity of 5 or 18 were
prepared. Various media were spherical and composed of
tungsten.
[0234] The plurality of prepared multilayer bodies were subjected
to surface treatment of the baked electrode layer with various
media and the surface treatment apparatus described above and
surface roughness Sa of the baked electrode layer was measured.
Surface roughness Sa was measured in the central portion of the end
surface, and an area of measurement was set to the inside of a
circle having a diameter of 0.2 mm.
[0235] With the medium having a diameter of 0.1 mm, in any case of
a specific gravity of 5 and 18, surface roughness Sa of the baked
electrode layer after surface treatment was not smaller than 500
nm. With the medium having a diameter of 2.5 mm, in any case of a
specific gravity of 5 and 18, surface roughness was not smaller
than 180 nm.
[0236] In contrast, with the medium having a diameter not smaller
than about 0.2 mm and not greater than about 2.0 mm, in any case of
a specific gravity of 5 and 18, surface roughness Sa of the baked
electrode layer after surface treatment was smaller than 180 nm. In
particular, by using a medium having a diameter not smaller than
about 0.4 mm and not greater than about 1.0 mm, surface roughness
Sa of the baked electrode layer after surface treatment was not
greater than 90 nm.
[0237] It was confirmed also experimentally from the results above
that the surface of the baked electrode layer could be reformed
when the medium was spherical, had a diameter not smaller than
about 0.2 mm and not greater than about 2.0 mm, and contained
tungsten.
[0238] It can be concluded that the surface of the baked electrode
layer is able to be reformed by setting a specific gravity of the
medium to be not lower than 5 and not higher than 18 under the
conditions above. It can additionally be concluded that the surface
of the baked electrode layer is able to further be reformed by
setting a diameter of the medium to be not smaller than about 0.4
mm and not greater than about 1.0 mm, for example.
[0239] FIG. 24 is a diagram showing one example of surface
roughness of the medium used in the second verification experiment.
Surface roughness of the medium used in the second verification
experiment is as shown in FIG. 24. Average surface roughness Sa
when the number of media to be measured was set to five was 40 nm
and a standard deviation .sigma.1 was 25 nm.
[0240] When a standard deviation was calculated again with
corrected average surface roughness Sa being defined as 46 nm in
consideration of variation in measurement, a standard deviation
.sigma.2 was approximately 29 nm. A value calculated by adding a
value five times as large as standard deviation .sigma.2 to
corrected average surface roughness Sa was set as the upper limit
of surface roughness Sa of the medium. In this case, the upper
limit of surface roughness Sa of the medium is approximately 191
nm. By setting surface roughness Sa of the medium to about 190 nm
or smaller, for example, the surface of the baked electrode layer
is able to be reformed as above.
[0241] The upper limit is a value serving as an index and a value
exceeding this value is not necessarily excluded. For example,
surface roughness Sa of the medium may be not greater than about
200 nm, for example.
[0242] In the first to third preferred embodiments described above,
an internal structure of the multilayer ceramic capacitor is not
limited to the structure disclosed in the first to third preferred
embodiments and can be modified as appropriate.
[0243] Though an example in which a resin layer is formed after the
baked electrode layer is subjected to surface treatment is
exemplified and described in the third preferred embodiment above,
limitation thereto is not intended and a resin layer may be formed
on the baked electrode layer before surface treatment of the baked
electrode layer and the resin layer may be subjected to surface
treatment. When the resin layer defines the surface of the
underlying electrode layer, the resin layer may be subjected to
surface treatment with a medium. In this case as well, the baked
electrode layer includes a first region which contains pores and
glass to a considerable extent and has cushioning properties so
that external impact applied to multilayer ceramic capacitor 10 can
be absorbed. Resistance to impact is thus improved.
[0244] As a result of surface treatment of the resin layer, the
surface of the resin layer is reformed and smoothened. The resin
layer is thus able to be satisfactorily be plated and attaching
properties of plating in a corner portion are prevented from being
deteriorated. Consequently, defective mounting in mounting of
multilayer ceramic capacitor 10 on a mount substrate is
significantly reduced or prevented.
[0245] The baked electrode layer may be subjected to surface
treatment and the resin layer may further be subjected to surface
treatment. Advantageous effects the same as described above are
obtained also in this case.
[0246] Although multilayer ceramic capacitors are described above
as examples of electronic components according to the first to
third preferred embodiments above, limitation thereto is not
intended and various electronic components including an external
electrode such as a piezoelectric component, a thermistor, or an
inductor are able to be adopted as an electronic component.
[0247] Features which can be combined may mutually be combined in
the description of the preferred embodiments above.
[0248] While preferred embodiments of the present invention have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing from the scope and spirit of the present invention. The
scope of the present invention, therefore, is to be determined
solely by the following claims.
* * * * *